View source for Polygonum humifusum subsp. caurianum

{{Treatment/ID
|accepted_name=Polygonum humifusum subsp. caurianum
|accepted_authority=(B. L. Robinson) Costea & Tardif
|publications={{Treatment/Publication
|title=Sida
|place=20: 995. 2003
|year=2003
}}
|common_names=Alaska knotweed;renouée du Nord-Ouest
|special_status={{Treatment/ID/Special_status
|code=E
|label=Endemic
}}
|basionyms={{Treatment/ID/Basionym
|name=Polygonum caurianum
|authority=B. L. Robinson
|rank=species
|publication_title=Proc. Boston Soc. Nat. Hist.
|publication_place=31: 264. 1904
}}
|synonyms=
|hierarchy=Polygonaceae;Polygonaceae subfam. Polygonoideae;Polygonum;Polygonum humifusum;Polygonum humifusum subsp. caurianum
|hierarchy_nav=<div class="higher-taxa"><div class="higher-taxon"><small>family</small>[[Polygonaceae]]</div><div class="higher-taxon"><small>subfamily</small>[[Polygonaceae subfam. Polygonoideae]]</div><div class="higher-taxon"><small>genus</small>[[Polygonum]]</div><div class="higher-taxon"><small>species</small>[[Polygonum humifusum]]</div><div class="higher-taxon"><small>subspecies</small>[[Polygonum humifusum subsp. caurianum]]</div></div>
|volume=Volume 5
|mention_page=page 548, 556
|treatment_page=page 555
}}<!--

--><span class="statement" id="st-undefined" data-properties=""><b>Plants </b>frequently reddish or purplish tinged; homophyllous or, rarely, heterophyllous. <b>Stems</b> prostrate, often zigzagged, branched mostly from base, wiry, 2–20(–40) cm. <b>Leaves</b> often opposite at proximal nodes; ocrea 2–3(–4) mm, proximal part funnelform, distal part soon lacerate, nearly completely deciduous; petiole 1–3.4 mm; blade usually reddish or purple tinged, obovate to oblanceolate, 3–12(–25) × (1.5–)2.5–4.5(–8) mm, margins flat, apex rounded to obtuse; stem leaves 1–1.5(–2) times as long as adjacent branch leaves, distal leaves overtopping flowers. <b>Inflorescences</b> axillary; cymes ± uniformly distributed, 2–6-flowered. <b>Pedicels</b> enclosed in ocreae, 0.5–1.5 mm. <b>Flowers</b> closed or semi-open; perianth 1.5–2.3(–3) mm; tube 28–49% of perianth length; tepals partially overlapping, green, margins pink, rarely white, petaloid, not keeled, oblong, ± outcurved, usually not cucullate; midveins unbranched or branched; stamens 5. <b>Achenes</b> exserted from perianth, dark brown to purple, ovate-lanceolate, 2–3-gonous, 1.4–1.6(–2.2) mm, faces unequal, apex not beaked or obscurely beaked, edges straight or concave, shiny or dull, smooth to roughened; late-season achenes common, 2–3.5 mm.</span><!--

-->{{Treatment/Body
|phenology=Flowering Jun–Aug.
|habitat=Gravel bars, waste places
|elevation=20-700 m
|distribution=N.W.T.;Nunavut;Yukon;Alaska.
|discussion=<p><i>Polygonum humifusum</i> often has opposite proximal leaves. In North America, the closest relative of <i></i>subsp.<i> caurianum</i> is <i>P. fowleri</i>, rare individuals of which produce opposite leaves.</p><!--
--><p>Three specimens of the Asian subsp. humifusum were collected near Nanaimo, Vancouver Island, by J. Macoun in 1883 and 1887 (J. F. Brenckle 1941); the subspecies has not been recollected there. It has stems and leaves that are green, and achenes 2.1–2.7 mm, ± beaked, and exserted 0.9–1.3 mm from the perianth at maturity.</p>
|tables=
|references=
}}<!--

--><!--

-->{{#Taxon:
name=Polygonum humifusum subsp. caurianum
|authority=(B. L. Robinson) Costea & Tardif
|rank=subspecies
|parent rank=species
|synonyms=
|basionyms=Polygonum caurianum
|family=Polygonaceae
|phenology=Flowering Jun–Aug.
|habitat=Gravel bars, waste places
|elevation=20-700 m
|distribution=N.W.T.;Nunavut;Yukon;Alaska.
|reference=None
|publication title=Sida
|publication year=2003
|special status=Endemic
|source xml=https://bibilujan@bitbucket.org/aafc-mbb/fna-data-curation.git/src/bb6b7e3a7de7d3b7888a1ad48c7fd8f5c722d8d6/coarse_grained_fna_xml/V5/V5_1134.xml
|subfamily=Polygonaceae subfam. Polygonoideae
|genus=Polygonum
|species=Polygonum humifusum
|subspecies=Polygonum humifusum subsp. caurianum
}}<!--

-->[[Category:Treatment]][[Category:Polygonum humifusum]]